Placental abruption

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The partial or complete separation of the placenta from the uterus prior to delivery; subsequent hemorrhage occurs from both maternal and fetal vessels.

Epidemiology

• Occurs most often in the third trimester

Etiology

• Vascular changes
  • Hypertension (most common cause)
  • Preeclampsia/eclampsia
• (Abdominal) trauma: e.g., car accidents, falls, intimate partner violence
• Twin pregnancy
• Sudden decrease in intrauterine pressure ; decompression of an overdistended uterus (e.g., ruptured membranes in polyhydramnios)
• Previous abruption, chorioamnionitis, short umbilical cord
• Maternal age: < 20 years and > 35 years
• Alcohol and cigarette consumption, cocaine use

Clinical features

• Maternal symptoms
  • Sudden onset of continuous vaginal bleeding (revealed abruptio placentae)
  • In up to 20% of cases, the hemorrhage is mainly retroplacental and vaginal bleeding does not occur (concealed abruptio placentae).
  • Sudden onset of abdominal pain or back pain
  • Uterine tenderness
• Fetal distress (60% of cases)
  • Decelerations on fetal heart monitor

Placenta previa

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Presence of the placenta in the lower uterine segment, which can lead to partial or full obstruction of the internal os; high risk of hemorrhage (rupture of placental vessels) and birth complications

Risk factors

• Maternal age > 35 years, multiparity, short intervals between pregnancies
• Previous curettage or cesarean delivery
• Previous placenta previa, previous/recurrent abortions

Classification

• Placenta previa: placenta either partially or completely covers the internal os
  • Previously, this category included marginal previa (placenta reaching the internal os), partial previa (placenta partially covering the internal os), and complete previa (placenta completely covering the internal os); these terms have been excluded from the new classification.
• Low-lying placenta: lower edge of the placenta lies less than 2 cm from the internal cervical os

Clinical features

• Sudden, painless, bright red vaginal bleeding
• Usually occurs during the 3rd trimester (before rupture of the membranes)
• Initial bleeding episodes are often self-limited and recur during the onset of labor
• Soft, nontender uterus
• Usually no fetal distress

Vasa previa

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Condition in which the fetal vessels are located in the membranes near the internal os of the cervix, putting them at risk of injury if the membranes rupture

Etiology

• Placental anomalies, such as:
  • Velamentous umbilical cord insertion
    • Inserts in chorioamniotic membrane rather than placenta → fetal vessels travel to placenta unprotected by Wharton jelly
  • Bilobate or succenturiate placenta
    • Variation of the placental morphology with one or more accessory lobes developing separately from the main placental body

Clinical features

• Painless vaginal bleeding (fetal blood) that occurs suddenly after rupture of membranes
• Fetal distress (e.g., fetal bradycardia; decelerations or sinusoidal pattern on fetal heart tracings)
• Fetal death can occur quickly through exsanguination or asphyxiation if fetal vessels are compressed during labor.